The present invention relates to a reflectance control method, for example, for controlling a reflectance of an optical recording medium and also relates to an optical recording medium having controlled reflectance.
An optical recording medium has been widely developed and utilized for the reason that the optical recording medium generally has a large memory capacitance and write-in or read-out operation can be performed in non-contact state, thus being advantageous for use.
A typical example of such optical recording medium is an optical disk, and there has been a tendency to standardize optical disks to standardize optical characteristics, mechanical characteristics and other characteristics thereof. For example, a reflectance or reflectance ratio, as one of the optical characteristics of a recording film of the optical recording medium is standardized to be within 10-90% before recording and 27-90% after recording, and the uniformity of the reflectance is also standardized to be less than .+-.12%.
Then, in a conventional technique for controlling the reflectance of optical recording media to accord with the predetermined standardized values, recording films are each formed by mixing different kinds of materials or a film thickness thereof is changed to control the reflectance.
However, such conventional technique for controlling the reflectance involves the following problems.
That is, first, in a reflectance control method in which a recording film is formed by a mixture of different kinds of materials, there is a case where the different materials are mutually internally reacted. In such case, it is impossible to mix the materials or it is necessary to control the reflectance in consideration of the internal reaction of the materials, thus being difficult to precisely control the reflectance.
Next, in a reflectance control method in which a thickness of the recording film is changed, it is difficult to uniformly the recording film so as to have a uniform thickness through an entire surface of the optical recording medium, thus making it also difficult to precisely control the reflectance.
In the above meanings, in the known art, there is not provided with an optical recording medium having an easily controllable or adjustable reflectance.